Wicking and coupling element(s) facilitating evaporative cooling of component(s)

ABSTRACT

A method is provided for facilitating cooling of electronic components of an electronic system. The method includes: providing a housing at least partially surrounding and forming a compartment about the components, and providing an immersion-cooling fluid is disposed within the compartment, at least one component of the electronic system being at least partially non-immersed within the fluid in the compartment; providing a wicking film element physically coupled to a main surface of the at least one component and partially disposed within the fluid within the compartment; and securing, via a coupling element, the wicking film element in physical coupling to the main surface of the at least one component without the coupling element overlying the main surface of the component(s). As an enhancement, the wicking film element wraps over the component to physically couple to two opposite main sides of the component.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. Ser. No. 13/627,256, filedSep. 26, 2012, and entitled “Wicking and Coupling Element(s)Facilitating Evaporative Cooling of Component(s)”, and which is herebyincorporated herein by reference in its entirety.

BACKGROUND

The power dissipation of integrated circuit chips, and the modulescontaining the chips, continues to increase in order, for instance, toachieve continued increase in processor performance. This trend posescooling challenges at the module and system levels.

In many large server applications, processors along with theirassociated electronics (e.g., memory, disk drives, power supplies, etc.)are packaged in removable drawer configurations stacked within anelectronics rack or frame comprising information technology (IT)equipment. In other cases, the electronics may be in fixed locationswithin the rack or frame. Typically, the components are cooled by airmoving in parallel airflow paths, usually front-to-back, impelled by oneor more air moving devices (e.g., fans or blowers). In some cases it maybe possible to handle increased power dissipation within a single draweror subsystem by providing greater airflow, for example, through the useof a more powerful air moving device or by increasing the rotationalspeed (i.e., RPMs) of an existing air moving device. However, thisapproach is becoming problematic, particularly in the context of acomputer center installation (i.e., data center).

The sensible heat load carried by the air exiting the rack is stressingthe capability of the room air-conditioning to effectively handle theload. This is especially true for large installations with “serverfarms” or large banks of computer racks located close together. In suchinstallations, liquid-cooling is an attractive technology to manage thehigher heat fluxes. The liquid absorbs the heat dissipated by thecomponents/modules in an efficient manner. Typically, the heat isultimately transferred from the liquid to an outside environment,whether air or other liquid.

BRIEF SUMMARY

The shortcomings of the prior art are overcome and additional advantagesare provided by, in one aspect, a method of facilitating cooling of anelectronic system is provided. The method includes: providing a housingat least partially surrounding and forming a compartment about multiplecomponents of the electronic system; providing a fluid disposed withinthe compartment, wherein an electronic component of the multiplecomponents is at least partially non-immersed within the fluid;providing a wicking film element physically coupled to a main surface ofthe electronic component and partially disposed within the fluiddisposed within the compartment; and securing, via a coupling element,the wicking film element in physical coupling with the main surface ofthe component without the coupling element overlying the main surface ofthe component.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

One or more aspects of the present invention are particularly pointedout and distinctly claimed as examples in the claims at the conclusionof the specification. The foregoing and other objects, features, andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 depicts one embodiment of a conventional raised floor layout ofan air-cooled computer installation;

FIG. 2 is a front elevational view of one embodiment of a liquid-cooledelectronics rack comprising multiple electronic systems to be cooled viaa cooling apparatus, in accordance with one or more aspects of thepresent invention;

FIG. 3 is a schematic of an electronic system of an electronics rack andone approach to liquid-cooling of an electronic component with theelectronic system, wherein the electronic component is indirectlyliquid-cooled by system coolant provided by one or more modular coolingunits disposed within the electronics rack, in accordance with one ormore aspects of the present invention;

FIG. 4 is a schematic of one embodiment of a modular cooling unit for aliquid-cooled electronics rack such as illustrated in FIG. 2, inaccordance with one or more aspects of the present invention;

FIG. 5 is a plan view of one embodiment of an electronic system layoutillustrating an air and liquid-cooling approach for cooling electroniccomponents of the electronic system, in accordance with one or moreaspects of the present invention;

FIG. 6A is an elevational view of an alternate embodiment of aliquid-cooled electronics rack with immersion-cooling of electronicsystems thereof, in accordance with one or more aspects of the presentinvention;

FIG. 6B is a cross-sectional elevational view of one immersion-cooledelectronic system of the liquid-cooled electronics rack of FIG. 6A, inaccordance with one or more aspects of the present invention;

FIG. 7A is a cross-sectional elevational view of one embodiment of apartial immersion-cooled electronic system for, for example, aliquid-cooled electronics rack, in accordance with one or more aspectsof the present invention;

FIG. 7B is a plan view of one embodiment of a condensate redirectstructure of the partial immersion-cooled electronic system of FIG. 7A,in accordance with one or more aspects of the present invention;

FIG. 8A is a cross-sectional elevational view of an alternate embodimentof a partial immersion-cooled electronic system for, for example, aliquid-cooled electronics rack, in accordance with one or more aspectsof the present invention;

FIG. 8B is a plan view of one embodiment of a condensate redirectstructure of the partial immersion-cooled electronic system of FIG. 8A,in accordance with one or more aspects of the present invention;

FIG. 9A is a cross-sectional elevational view of another embodiment of apartial immersion-cooled electronic system for, for example, aliquid-cooled electronics rack, in accordance with one or more aspectsof the present invention;

FIG. 9B is a plan view of one embodiment of a condensate redirectstructure of the partial immersion-cooled electronic system of FIG. 9A,in accordance with one or more aspects of the present invention;

FIG. 10 is an elevational view of one embodiment of a liquid-cooledelectronics rack with partial immersion-cooling of electronic systemsthereof, in accordance with one or more aspects of the presentinvention;

FIG. 11 is a cross-sectional elevational view of another embodiment of apartial immersion-cooled electronic system for, for example, aliquid-cooled electronics rack, in accordance with one or more aspectsof the present invention;

FIG. 12A is an end elevational view of one embodiment of a componentcomprising a component board and multiple chips disposed on oppositesides of the component board, with wicking film elements affixed to thechips on the component board, in accordance with one or more aspects ofthe present invention;

FIG. 12B is a top plan view of the structure of FIG. 12A, in accordancewith one or more aspects of the present invention;

FIG. 13A is an end elevational depiction of another embodiment of acomponent comprising a component board with multiple chips disposed onopposite sides thereof and a wicking film element wrapped over thecomponent board and chips, and held in place via one embodiment of acoupling element, in accordance with one or more aspects of the presentinvention;

FIG. 13B is a side elevational view of the structure of FIG. 13A, inaccordance with one or more aspects of the present invention;

FIG. 14A is an end elevational depiction of another embodiment of acomponent comprising a component board with multiple chips disposed onopposite sides thereof and a wicking film element wrapped over thecomponent board and chips, and held in place via another embodiment of acoupling element, in accordance with one or more aspects of the presentinvention;

FIG. 14B is a side elevational view of the structure of FIG. 14A, inaccordance with one or more aspects of the present invention;

FIG. 15A is an end elevational depiction of another embodiment of acomponent comprising a component board with multiple chips disposed onopposite sides thereof and a first, shaped wicking film elementphysically coupled to a first side thereof and a second, shaped wickingfilm element physically coupled to a second side thereof, and maintainedin position via multiple coupling elements, in accordance with one ormore aspects of the present invention;

FIG. 15B is a side elevational view of the structure of FIG. 15A, inaccordance with one or more aspects of the present invention; and

FIG. 15C is a cross-sectional view of the structure of FIGS. 15A & 15B,taken along line 15C-15C in FIG. 15B, and illustrating first and secondshaped, wicking film elements differently configured to accommodatedifferently-sized and spaced chips on the opposite main sides of thecomponent board, in accordance with one or more aspects of the presentinvention.

DETAILED DESCRIPTION

As used herein, the terms “electronics rack”, “rack-mounted electronicequipment”, and “rack unit” are used interchangeably, and unlessotherwise specified include any housing, frame, rack, compartment, bladeserver system, etc., having one or more heat-generating components of acomputer system, electronic system, or information technology equipment,and may be, for example, a stand alone computer processor having high-,mid- or low-end processing capability. In one embodiment, an electronicsrack may comprise a portion of an electronic system, a single electronicsystem, or multiple electronic systems, for example, in one or moresub-housings, blades, books, drawers, nodes, compartments, etc., havingone or more heat-generating electronic components disposed therein. Anelectronic system(s) within an electronics rack may be movable or fixed,relative to the electronics rack, with rack-mounted electronic drawersand blades of a blade center system being two examples of electronicsystems (or subsystems) of an electronics rack to be cooled.

“Electronic component” or “component” refers to any heat generatingcomponent of, for example, a computer system or other electronics unitrequiring cooling. By way of example, an electronic component maycomprise one or more integrated circuit dies and/or other electronicdevices to be cooled, including one or more processor dies, memory diesor memory support dies. As a further example, the electronic componentmay comprise one or more bare dies or one or more packaged dies disposedon a common carrier. Further, unless otherwise specified herein, theterms “liquid-cooled cold plate”, “liquid-cooled base plate”, or“liquid-cooled structure” each refer to any conventional thermallyconductive structure having a plurality of channels or passagewaysformed therein for flowing of liquid-coolant therethrough.

As used herein, a “liquid-to-liquid heat exchanger” may comprise, forexample, two or more coolant flow paths, formed of thermally conductivetubing (such as copper or other tubing) in thermal or mechanical contactwith each other. Size, configuration and construction of theliquid-to-liquid heat exchanger can vary without departing from thescope of the invention disclosed herein. Further, “data center” refersto a computer installation containing one or more electronics racks tobe cooled. As a specific example, a data center may include one or morerows of rack-mounted computing units, such as server units.

One example of facility coolant and system coolant is water. However,the concepts disclosed herein are readily adapted to use with othertypes of coolant on the facility side and/or on the system side. Forexample, one or more of these coolants may comprise a brine, adielectric liquid, a fluorocarbon liquid, a liquid metal, or othersimilar coolant, or a refrigerant, while still maintaining theadvantages and unique features of the present invention.

Reference is made below to the drawings, which are not drawn to scalefor ease of understanding of the various aspects of the presentinvention, wherein the same reference numbers used throughout differentfigures designate the same or similar components.

As shown in FIG. 1, in a raised floor layout of an air-cooled datacenter 100 typical in the prior art, multiple electronics racks 110 aredisposed in one or more rows. A computer installation such as depictedin FIG. 1 may house several hundred, or even several thousandmicroprocessors. In the arrangement of FIG. 1, chilled air enters thecomputer room via floor vents from a supply air plenum 145 definedbetween the raised floor 140 and a base or sub-floor 165 of the room.Cooled air is taken in through louvered covers at air inlet sides 120 ofthe electronics racks and expelled through the backs, i.e., air outletsides 130, of the electronics racks. Each electronics rack 110 may haveone or more air-moving devices (e.g., fans or blowers) to provide forcedinlet-to-outlet air flow to cool the electronic components within thedrawer(s) of the rack. The supply air plenum 145 provides conditionedand cooled air to the air-inlet sides of the electronics racks viaperforated floor tiles 160 disposed in a “cold” aisle of the computerinstallation. The conditioned and cooled air is supplied to plenum 145by one or more air conditioning units 150, also disposed within datacenter 100. Room air is taken into each air conditioning unit 150 nearan upper portion thereof. This room air may comprise (in part) exhaustedair from the “hot” aisles of the computer installation defined byopposing air outlet sides 130 of the electronics racks 110.

FIG. 2 depicts one embodiment of a liquid-cooled electronics rack 200comprising a cooling apparatus. In one embodiment, liquid-cooledelectronics rack 200 comprises a plurality of electronic systems 210,which may be processor or server nodes (in one embodiment). A bulk powerassembly 220 is disposed at an upper portion of liquid-cooledelectronics rack 200, and two modular cooling units (MCUs) 230 arepositioned in a lower portion of the liquid-cooled electronics rack forproviding system coolant to the electronic systems. In the embodimentsdescribed herein, the system coolant is assumed to be water or anaqueous-based solution, by way of example only.

In addition to MCUs 230, the cooling apparatus depicted includes asystem coolant supply manifold 231, a system coolant return manifold232, and manifold-to-node fluid connect hoses 233 coupling systemcoolant supply manifold 231 to electronic subsystems 210 (for example,to cold plates or liquid-cooled vapor condensers (see FIGS. 6A-9B)disposed within the systems) and node-to-manifold fluid connect hoses234 coupling the individual electronic systems 210 to system coolantreturn manifold 232. Each MCU 230 is in fluid communication with systemcoolant supply manifold 231 via a respective system coolant supply hose235, and each MCU 230 is in fluid communication with system coolantreturn manifold 232 via a respective system coolant return hose 236.

Heat load of the electronic systems 210 is transferred from the systemcoolant to cooler facility coolant within the MCUs 230 provided viafacility coolant supply line 240 and facility coolant return line 241disposed, in the illustrated embodiment, in the space between raisedfloor 145 and base floor 165.

FIG. 3 schematically illustrates one cooling approach using the coolingapparatus of FIG. 2, wherein a liquid-cooled cold plate 300 is showncoupled to an electronic component 301 of an electronic system 210within the liquid-cooled electronics rack 200. Heat is removed fromelectronic component 301 via system coolant circulating via pump 320through liquid-cooled cold plate 300 within the system coolant loopdefined, in part, by liquid-to-liquid heat exchanger 321 of modularcooling unit 230, hoses 235, 236 and cold plate 300. The system coolantloop and modular cooling unit are designed to provide coolant of acontrolled temperature and pressure, as well as controlled chemistry andcleanliness to the electronic systems. Furthermore, the system coolantis physically separate from the less controlled facility coolant inlines 240, 241, to which heat is ultimately transferred.

FIG. 4 depicts one detailed embodiment of a modular cooling unit 230. Asshown in FIG. 4, modular cooling unit 230 includes a facility coolantloop, wherein building chilled, facility coolant is provided (via lines240, 241) and passed through a control valve 420 driven by a motor 425.Valve 420 determines an amount of facility coolant to be passed throughheat exchanger 321, with a portion of the facility coolant possiblybeing returned directly via a bypass orifice 435. The modular coolingunit further includes a system coolant loop with a reservoir tank 440from which system coolant is pumped, either by pump 450 or pump 451,into liquid-to-liquid heat exchanger 321 for conditioning and outputthereof, as cooled system coolant to the electronics rack to be cooled.Each modular cooling unit is coupled to the system supply manifold andsystem return manifold of the liquid-cooled electronics rack via thesystem coolant supply hose 235 and system coolant return hose 236,respectively.

FIG. 5 depicts another cooling approach, illustrating one embodiment ofan electronic system 210 component layout wherein one or more air movingdevices 511 provide forced air flow 515 in normal operating mode to coolmultiple electronic components 512 within electronic system 210. Coolair is taken in through a front 531 and exhausted out a back 533 of thedrawer. The multiple components to be cooled include multiple processormodules to which liquid-cooled cold plates 520 are coupled, as well asmultiple arrays of memory modules 530 (e.g., dual in-line memory modules(DIMMs)) and multiple rows of memory support modules 532 (e.g., DIMMcontrol modules) to which air-cooled heat sinks may be coupled. In theembodiment illustrated, memory modules 530 and the memory supportmodules 532 are partially arrayed near front 531 of electronic system210, and partially arrayed near back 533 of electronic system 210. Also,in the embodiment of FIG. 5, memory modules 530 and the memory supportmodules 532 are cooled by air flow 515 across the electronics system.

The illustrated cooling apparatus further includes multiplecoolant-carrying tubes connected to and in fluid communication withliquid-cooled cold plates 520. The coolant-carrying tubes comprise setsof coolant-carrying tubes, with each set including (for example) acoolant supply tube 540, a bridge tube 541 and a coolant return tube542. In this example, each set of tubes provides liquid-coolant to aseries-connected pair of cold plates 520 (coupled to a pair of processormodules). Coolant flows into a first cold plate of each pair via thecoolant supply tube 540 and from the first cold plate to a second coldplate of the pair via bridge tube or line 541, which may or may not bethermally conductive. From the second cold plate of the pair, coolant isreturned through the respective coolant return tube 542.

As computing demands continue to increase, heat dissipation requirementsof electronic components, such as microprocessors and memory modules,are also rising. This has motivated the development of the applicationof single-phase, liquid-cooling solutions such as described above.Single-phase, liquid-cooling, however, has some issues. Sensible heatingof the liquid as it flows along the cooling channels and acrosscomponents connected in series results in a temperature gradient. Tomaintain a more uniform temperature across the heat-generatingcomponent, the temperature change in the liquid needs to be minimized.This requires the liquid to be pumped at higher flow rates, consumingmore pump power, and thus leading to a less efficient system. Further,it is becoming increasingly challenging to cool all the heat sources ona server or electronic system using pumped liquid, due to the densityand number of components, such as controller chips, I/O components andmemory modules. The small spaces and number of components to be cooledmake liquid plumbing a complex design and fabrication problem andsignificantly raises the overall cost of the cooling solution.

Immersion-cooling is one possible solution to these issues. Inimmersion-cooling, components to be cooled are immersed in a dielectricfluid that dissipates heat through boiling. The vapor is then condensedby a secondary, rack-level working (or system) fluid using node ormodule-level, finned condensers, as explained below.

Direct immersion-cooling of electronic components of an electronicsystem of the rack unit using dielectric fluid (e.g., a liquiddielectric coolant) advantageously avoids forced air cooling and enablestotal liquid-cooling of the electronics rack within the data center.Although indirect liquid-cooling, such as described above in connectionwith FIGS. 3 and 5, has certain advantages due to the low cost and wideavailability of water as a coolant, as well as its superior thermal andhydraulic properties, where possible and viable, the use of dielectricfluid immersion-cooling may offer several unique benefits.

For example, the use of a dielectric fluid that condenses at atemperature above typical outdoor ambient air temperature would enabledata center cooling architectures which do not require energy intensiverefrigeration chillers. Yet other practical advantages, such as theability to ship a coolant filled electronic subsystem, may offer benefitover water-cooled approaches such as depicted in FIGS. 3 & 5, whichrequire shipping dry and the use of a fill and drain protocol to insureagainst freeze damage during transport. Also, the use of liquidimmersion-cooling may, in certain cases, allow for greater compaction ofelectronic components at the electronic subsystem level and/orelectronic rack level since conductive cooling structures might beeliminated. Unlike corrosion sensitive water-cooled systems, chemicallyinert dielectric coolant (employed with an immersion-cooling approachsuch as described herein) would not mandate copper as the primarythermally conductive wetted metal. Lower cost and lower mass aluminumstructures could replace copper structures wherever thermally viable,and the mixed wetted metal assemblies would not be vulnerable togalvanic corrosion, such as in the case of a water based coolingapproach. For at least these potential benefits, dielectric fluidimmersion-cooling of one or more electronic systems of an electronicsrack may offer significant energy efficiency and higher performancecooling benefits, compared with currently available hybrid air andindirect water cooled systems.

In the examples discussed below, the dielectric fluid may comprise anyone of a variety of commercially available dielectric coolants. Forexample, any of the Fluorinert™ or Novec™ fluids manufactured by 3MCorporation (e.g., FC-72, FC-86, HFE-7000, and HFE-7200) could beemployed. Alternatively, a refrigerant such as R-134a or R-245fa may beemployed if desired.

FIG. 6A is a schematic of one embodiment of a liquid-cooled electronicsrack, generally denoted 600, employing immersion-cooling of electronicsystems, in accordance with an aspect of the present invention. Asshown, liquid-cooled electronics rack 600 includes an electronics rack601 containing a plurality of electronic systems 610 disposed, in theillustrated embodiment, horizontally so as to be stacked within therack. By way of example, each electronic system 610 may be a server unitof a rack-mounted plurality of server units. In addition, eachelectronic system includes multiple electronic components to be cooled,which in one embodiment, comprise multiple different types of electroniccomponents having different heights and/or shapes within the electronicsystem.

The cooling apparatus is shown to include one or more modular coolingunits (MCU) 620 disposed, by way of example, in a lower portion ofelectronics rack 601. Each modular cooling unit 620 may be similar tothe modular cooling unit depicted in FIG. 4, and described above. Themodular cooling unit includes, for example, a liquid-to-liquid heatexchanger for extracting heat from coolant flowing through a systemcoolant loop 630 of the cooling apparatus and dissipating heat within afacility coolant loop 619, comprising a facility coolant supply line 621and a facility coolant return line 622. As one example, facility coolantsupply and return lines 621, 622 couple modular cooling unit 620 to adata center facility coolant supply and return (not shown). Modularcooling unit 620 further includes an appropriately sized reservoir, pumpand optional filter for moving liquid-coolant under pressure throughsystem coolant loop 630. In one embodiment, system coolant loop 630includes a coolant supply manifold 631 and a coolant return manifold632, which are coupled to modular cooling unit 620 via, for example,flexible hoses. The flexible hoses allow the supply and return manifoldsto be mounted within, for example, a door of the electronics rackhingedly mounted to the front or back of the electronics rack. In oneexample, coolant supply manifold 631 and coolant return manifold 632each comprise an elongated rigid tube vertically mounted to theelectronics rack 601 or to a door of the electronics rack.

In the embodiment illustrated, coolant supply manifold 631 and coolantreturn manifold 632 are in fluid communication with respective coolantinlets 635 and coolant outlets 636 of individual sealed housings 640containing the electronic systems 610. Fluid communication between themanifolds and the sealed housings is established, for example, viaappropriately sized, flexible hoses 633, 634. In one embodiment, eachcoolant inlet 635 and coolant outlet 636 of a sealed housing is coupledto a respective liquid-cooled vapor condenser 650 disposed within thesealed housing 640. Heat removed from the electronic system 610 via therespective liquid-cooled vapor condenser 650 is transferred from thesystem coolant via the coolant return manifold 632 and modular coolingunit 620 to facility coolant loop 619. In one example, coolant passingthrough system coolant loop 630, and hence, coolant passing through therespective liquid-cooled vapor condensers 650 is water.

Note that, in general, fluidic coupling between the electronicsubsystems and coolant manifolds, as well as between the manifolds andthe modular cooling unit(s) can be established using suitable hoses,hose barb fittings and quick disconnect couplers. In the exampleillustrated, the vertically-oriented coolant supply and return manifolds631, 632 each include ports which facilitate fluid connection of therespective coolant inlets and outlets 635, 636 of the housings(containing the electronic subsystems) to the manifolds via the flexiblehoses 633, 634. Respective quick connect couplings may be employed tocouple the flexible hoses to the coolant inlets and coolant outlets ofthe sealed housings to allow for, for example, removal of a housing andelectronic subsystem from the electronics rack. The quick connectcouplings may be any one of various types of commercial availablecouplings, such as those available from Colder Products Co. of St. Paul,Minn., USA or Parker Hannifin of Cleveland, Ohio, USA.

One or more hermetically sealed electrical connectors 648 may also beprovided in each sealed housing 640, for example, at a back surfacethereof, for docking into a corresponding electrical plane (not shown)of the electronics rack in order to provide electrical and networkconnections 649 to the electronic system disposed within the sealedhousing when the electronic system is operatively positioned within thesealed housing and the sealed housing is operatively positioned withinthe electronics rack.

As illustrated in FIG. 6B, electronic system 610 comprises a pluralityof electronic components 642, 643 of different height and type on asubstrate 641, and is shown within sealed housing 640 with the pluralityof electronic components 642, 643 immersed within a dielectric fluid645. Sealed housing 640 is configured to at least partially surround andform a sealed compartment about the electronic system with the pluralityof electronic components 642, 643 disposed within the sealedcompartment. In an operational state, dielectric fluid 645 pools in theliquid state at the bottom of the sealed compartment and is ofsufficient volume to submerge the electronic components 642, 643. Theelectronic components 642, 643 dissipate varying amounts of power, whichcause the dielectric fluid to boil, releasing dielectric fluid vapor,which rises to the upper portion of the sealed compartment of thehousing.

The upper portion of sealed housing 640 is shown in FIG. 6B to includeliquid-cooled vapor condenser 650. Liquid-cooled vapor condenser 650 isa thermally conductive structure which includes a liquid-cooled baseplate 652, and a plurality of thermally conductive condenser fins 651extending therefrom in the upper portion of the sealed compartment. Aplenum structure 654 comprises part of liquid-cooled base plate 652, andfacilitates passage of system coolant through one or more channels inthe liquid-cooled base plate 652. In operation, the dielectric fluidvapor contacts the cool surfaces of the thermally conductive condenserfins and condenses back to liquid phase, dropping downwards towards thebottom of the sealed compartment.

System coolant supplied to the coolant inlet of the housing passesthrough the liquid-cooled base plate of the liquid-cooled vaporcondenser and cools the solid material of the condenser such thatcondenser fin surfaces that are exposed within the sealed compartment tothe dielectric fluid vapor (or the dielectric fluid itself) are wellbelow saturation temperature of the vapor. Thus, vapor in contact withthe cooler condenser fin surfaces will reject heat to these surfaces andcondense back to liquid form. Based on operating conditions of theliquid-cooled vapor condenser 650, the condensed liquid may be close intemperature to the vapor temperature or could be sub-cooled to a muchlower temperature.

Advantageously, in immersion-cooling, all of the components to be cooledare immersed in the dielectric fluid. The system fluid can tolerate alarger temperature rise, while maintaining component temperatures, thusallowing a lower flow rate, and higher inlet temperatures, improvingenergy efficiency of the resultant cooling apparatus. However, two-phaseimmersion-cooling enclosures may require a large volume of dielectricfluid to completely cover the variously configured components within thesystem, including (for example) dual in-line memory modules (DIMMs),graphics boards, solid state drives (SSDs), and processors with tallheat spreader fins attached. This need for a large amount of dielectricfluid increases both the weight and the cost of the cooling solution.Disclosed hereinbelow with reference to FIGS. 7A-10 are alternateembodiments of a cooling apparatus, wherein partial immersion-cooling isemployed in combination with a condensate redirect structure, whichpreferentially redirects condensate drip onto selected, non-immersedelectronic components or portions thereof of the electronic system.These non-immersed components may be taller electronic components thatare only partially immersed, or may even be electronic componentssuspended within the electronic system such that they are completelynon-immersed within the dielectric fluid. The cooling apparatuses andmethods disclosed herein facilitate partial immersion-cooling ofelectronic components of an electronic system, and therebyadvantageously reduce the amount of dielectric fluid required within thesystem compared with a full immersion-cooling approach described abovein connection with FIGS. 6A-6B.

By way of example, the cooling apparatus includes a housing at leastpartially surrounding and forming a compartment about multipleelectronic components to be cooled, and a fluid disposed within thecompartment. A first electronic component of the multiple electroniccomponents is at least partially non-immersed within the fluid, and asecond electronic component of the multiple electronic components is atleast partially non-immersed within the fluid, wherein the first andsecond electronic components are different types of electroniccomponents with different configurations. The cooling apparatus furtherincludes a vapor condenser comprising a vapor-condensing surfacedisposed at least partially in a vapor region of the compartment forcondensing fluid vapor, and a condensate redirect structure disposedwithin the compartment at least partially between the vapor condenserand the first and second electronic components. The condensate redirectstructure is differently configured over the first electronic componentcompared with over the second electronic component, and provides adifferent pattern of condensate drip over the first electronic componentcompared with over the second electronic component.

In certain embodiments, the condensate redirect structure of the coolingapparatus may comprise different patterns of condensate drip openingsover the first electronic component compared with over the secondelectronic component, or the condensate redirect structure may comprisedifferently configured condensate drip openings over the firstelectronic component compared with over the second electronic component.The first electronic component may be a higher-heat-generatingelectronic component than the second electronic component, and in thatcase, the condensate redirect structure facilitates greater condensatedrip over the first electronic component compared with over the secondelectronic component. Thus, the condensate redirect structure mayinclude, for instance, different patterns of condensate drip openingsover the first and second electronic components, or differentlyconfigured condensate drip openings over the first and second electroniccomponents, with the different pattern of condensate drip over the firstelectronic component compared with over the second electronic componentbeing correlated, at least in part, to the different configurations ofthe first electronic component and the second electronic component.

By way of detailed example, FIGS. 7A & 7B depict a first coolingapparatus embodiment wherein the condensate redirect structure comprisesa vapor-permeable, liquid-phobic material with a plurality of condensatedrip openings disposed in different, sloped regions of the structure.These condensate drip openings may be differently shaped openings thatfacilitate, at least in part, a desired pattern of condensate drippingonto differently configured electronic components to be cooled.

In an alternate embodiment, the condensate redirect structure of thecooling apparatus may comprise a mesh structure with multiple condensatedrip pans supported by the mesh structure. One embodiment of thisconfiguration is depicted in FIGS. 8A-8B. In this configuration, and byway of example, a first condensate drip pan of the multiple condensatedrip pans is configured to provide a first pattern of condensate driponto the first electronic component, and a second condensate drip pan ofthe multiple condensate drip pans is configured to provide a secondpattern of condensate drip onto the second electronic component, whereinthe first pattern of condensate drip and the second pattern ofcondensate drip are different patterns of condensate drip. Further,vapor condenser condensing surfaces may be physically and/or chemicallymodified to, for example, increase condensation and condensate drip overselected regions of the electronic system.

In another embodiment, the condensate redirect structure of the coolingapparatus may be suspended at an angle within the compartment tofacilitate the flow of condensate drops along the suspended condensateredirect structure. In this embodiment, the suspended condensateredirect structure includes a drip pan with a plurality of condensatedrip openings, wherein multiple condensate drip openings of theplurality of condensate drip openings are aligned over, for example, thefirst and second electronic components. In addition, in this embodiment,the vapor condenser may include one or more sloped, thermally conductivefins which facilitate movement of condensed coolant drops in a firstdirection for dripping onto the condensate redirect structure at a firstside or other desired region thereof. In combination with this, thecondensate redirect structure may be suspended at an angle to facilitatemovement of the condensed coolant drops in a second direction along thecondensate redirect structure, wherein the second direction is differentfrom the first direction. In one embodiment, the second direction isopposite to the first direction.

Advantageously, the condensate redirect structure of the coolingapparatus is a shaped, porous structure disposed between the vaporcondenser and the electronic components being cooled. The condensatedrip structure facilitates collecting condensed coolant drops, anddripping the condensate preferentially over, for example, the at leastpartially non-immersed electronic components of the electronic system,which may include DIMMs, graphics and network cards, solid state drives,heat-spreader extended surfaces, etc. The condensed coolant drips ontothese partially non-immersed electronic components, with most of thecoolant making its way back into the pool of dielectric fluid at thelower region of the compartment, and with some of the condensate dripcontacting the non-immersed portions of the electronic componentevaporating directly, and thus cooling the heated, non-immersedelectronic component, or portion thereof extending from the dielectricfluid. Thus, a smaller fill height of dielectric coolant is required,and less volume of dielectric coolant is needed in this partialimmersion-cooling implementation. This reduction in coolant fluid helpsto reduce the cost and weight of the immersion-cooling solution. Inaddition to this specific advantage, an immersion-cooling solution hasseveral inherent advantages, including improved temperature uniformityacross the various components, lower required flow rate of the systemcoolant, and potential for warm water-cooling. The latter advantageimproves energy efficiency, and may enable the use of economizers.

FIG. 7A is a cross-sectional elevational view of one embodiment of acooled electronic system, generally denoted 700, comprising a coolingapparatus in accordance with one or more aspects of the presentinvention. In one embodiment, the cooling apparatus may be configured toaccommodate an electronic system (or node) of an electronics rack, suchas described above in connection with FIGS. 6A & 6B. In such anembodiment, a rack-level inlet manifold and rack-level outlet manifoldwould facilitate distribution of system liquid coolant 711 through theliquid-cooled vapor condenser 710 of the cooling apparatuses associatedwith the electronic systems of the electronics rack (as describedfurther below in relation to the example of rack unit of FIG. 10).Further, depending upon the implementation, there may be a singlecooling apparatus for an electronic system cooling, for instance,substantially the entire electronic system or multiple such coolingapparatuses within the electronic system, for example, to separatelycool different electronic components thereof.

As illustrated in FIG. 7A, liquid-cooled vapor condenser 710 includes(in this example) a plurality of thermally conductive fins 712, whichcomprise one or more vapor-condensing surfaces disposed at leastpartially in a vapor region of a compartment 720 defined by a housing702 at least partially surrounding and forming compartment 720 aboutmultiple differently-sized electronic components 721, 722, 723, 724,etc., to be cooled. The vapor condenser, with the plurality of thermallyconductive condenser fins 712 facilitates condensing of fluid vaporrising to the upper region of compartment 720. Housing 702 is mounted,in this example, to a substrate 701, such as a printed circuit board, towhich the plurality of electronic components to be cooled, are attached.Attachment mechanisms 705 (e.g., screws) and gasket seals 706 facilitateforming a fluid-tight compartment about the electronic components. Afluid 730, such as a dielectric fluid, only partially fills compartment720. By way of example, the fluid may fill less than 50% of thecompartment. Note that in the example of FIG. 7A, the multipledifferently-sized electronic components 721, 722, 723, 724, etc., may befully immersed, partially immersed, partially non-immersed, or fullynon-immersed, within the dielectric fluid. In one implementation, theseelectronic components may be different types of electronic components,with different configurations. A sealable fill port 703 may be providedwithin housing 702 to facilitate adding dielectric fluid to thecompartment.

In the example of FIG. 7A, the cooling apparatus further includes acondensate redirect structure 740, which in this embodiment, comprises avapor-permeable, liquid-phobic material 741. In one embodiment, thisliquid-phobic material may be formed as a laminate structure andcomprise, as illustrated in FIG. 7B, multiple sloped regions 742. Thesesloped regions angle inwards and downwards from adjoining interfaces 743between regions towards respective condensate drip openings 744 a, 744b, 744 c, 744 d, 744 e, & 744 f, which are differently configured inthis example. Advantageously, the condensate drip openings within thedifferent regions are configured and/or patterned to facilitatecondensate preferentially dripping onto underlying electronic componentsthat are non-immersed within the dielectric fluid 730. By way ofexample, electronic component 721 may comprise dual in-line memorymodules (DIMMs), which are cards upon which memory modules are affixed.These DIMMs are tall, thin elongate structures, and condensate dripopenings 744 a in condensate drip structure 740 are sized and configuredto correlate, at least in part, to the configuration of the underlyingelectronic component 721 to be cooled. Similarly, condensate dripopenings 744 b, 744 c, 744 d, 744 e, & 744 f are, in one embodiment,sized and configured to provide a desired pattern of condensate dripover the underlying, partially non-immersed electronic component(s) tobe cooled.

As noted, the condensate redirect structure facilitates increasingcondensate drip over certain regions, or more particularly, certaincomponents of the electronic system. The structure may be fabricated, inone embodiment, with a shaped, porous coolant-impermeable,vapor-permeable sheet material. The sheet material may be shaped intoslight cones, which terminate at the condensate drip openings (e.g.,holes, slots, etc.) over the taller (or suspended), at least partiallynon-immersed electronic components to be cooled to allow the condensatedripping from the vapor condenser to preferentially drip over thenon-immersed components. Advantageously, substantially all condensate isdirected (in this embodiment) where desired by the condensate redirectstructure.

The angled shaping of the vapor-permeable redirect surfaces shown inFIGS. 7A & 7B is exaggerated, with only a slight amount of shapingactually required in order for the condensate drops to flow along thecondensate redirect structure to the condensate drip openings. The sizesof the different sloped regions helps to control the distribution of thecondensate drip fluid, with hotter electronic components requiring alarger collection area so that a larger amount of condensate drip isprovided over those electronic components. The use of a porousvapor-permeable sheet material allows the fluid vapor rising from theheated components to flow through the sheet and reach the vaporcondenser disposed in the upper region of the compartment, but the sheetimpedes the passage of the condensate drops dripping back from thethermally conductive condenser fins. Thus, vapor can generally flowthrough the entire sheet material of the condensate redirect structure,but the condensed drops can only flow back through the condensate dripopenings provided within the material. By way of example the porousmaterial could comprise PTFE, nylon, polycarbonate, polypropylene, etc.Such materials are available as thin, flexible sheets, and the shapingof the sloped regions could be achieved through heat treatment oflaminated versions of these films, where the laminate provides thenecessary mechanical stiffness, or through suspension of the native filmon an appropriately shaped mesh structure, such as a metal mesh.

Also provided, by way of example only, are heaters 725 immersed withindielectric fluid 730 in the cooling apparatus embodiments depicted inFIGS. 7A-9B. In one implementation, heaters 725 may be provided adjacentto, for example, the one or more at least partially non-immersedelectronic components within the compartment in order to initiate morequickly vaporization of fluid, and thus, condensate dripping in theregion of the non-immersed electronic components. If employed, heaters725 could be cycled on for a short time upon initiation of operation ofthe electronic system to start the cooling cycle described herein.

FIGS. 8A-9B depict alternate embodiments of the cooling apparatusdescribed above in connection with FIGS. 7A & 7B. Configuration andoperation of these cooling apparatuses is similar to that describedabove in connection with FIGS. 7A & 7B, unless noted otherwise below.

Cooled electronic system 800 of FIGS. 8A & 8B includes a coolingapparatus comprising a liquid-cooled vapor condenser 810 with one ormore channels to facilitate flow of liquid coolant 811 therethrough.Vapor condenser 810 further includes, in this embodiment, differentpatterns of thermally conductive condenser fins 812, which define one ormore vapor-condensing surfaces disposed at least partially in a vaporregion of compartment 720 defined by housing 702 partially surroundingand forming compartment 720 about multiple differently-sized electroniccomponents 721, 722, 723, 724, etc., to be cooled. The vapor condenser810, with the plurality of patterns of thermally conductive condenserfins 812, facilitates condensing of vapor fluid rising to the upperregion of compartment 720. In one embodiment, the different patterns ofcondenser fins 812 comprise different physical configurations and/ornumbers of condenser fins, which provide different densities of surfaceareas that are aligned, in this embodiment, over respective drip pans842 of a condensate redirect structure 840. If desired, one or more ofthe fins in one or more selected fin patterns may also be chemicallymodified to increase condensate drip where needed.

As illustrated in FIGS. 8A & 8B, condensate redirect structure 840includes, in one embodiment, a mesh structure 841 with a plurality ofcondensate drip pans 842 a, 842 b, 842 c, 842 d, 842 e, & 842 f,supported by the mesh structure 841. The condensate drip pans 842 a-842f (in this example) may be of different sizes and configurations, asillustrated in FIG. 8B. One or more condensate drip openings 844 a-844f, respectively, are provided within condensate drip pans 842 a-842 f.These openings are configured and positioned to provide a desiredpattern of condensate drip onto the underlying at least partiallynon-immersed electronic component to be cooled. The configuration andnumber of condensate drip openings 844 a-844 f may correspond, in oneembodiment, to the underlying configuration of the at least partiallynon-immersed electronic component being cooled by the condensate drip.Accumulating of condensate drops within the condensate drip pans 842a-842 f is facilitated by the above-noted, different patterns ofthermally conductive condenser fins 812 of the vapor condenser.

As a specific example, a first condensate drip pan of the multiplecondensate drip pans may be configured to facilitate a first pattern ofcondensate drip onto a first electronic component (e.g., electroniccomponent 721), and a second condensate drip pan of the multiplecondensate drip pans may be configured to facilitate a second pattern ofcondensate drip onto a second electronic component (e.g., electroniccomponent 722) of the electronic system. In this example the firstpattern of condensate drip and the second pattern of condensate drip aredifferent patterns of condensate drip, as can be ascertained from thecondensate drip openings depicted in the respective condensate drip pansillustrated in the example of FIG. 8B. The different patterns ofthermally conductive condenser fins over the different condensate drippans further facilitates accumulation of condensate drip within therespective, differently-sized condensate drip pans. In this embodiment,mesh structure 841 advantageously facilitates rise of fluid vapor withinthe compartment, but any condensate drip outside of the condensate drippans will drop through mesh structure 841.

In one example, mesh structure 841 may be a metal mesh, and theindividual-shaped condensate drip pans may be suspended on the meshstructure. Vaporized coolant flows around the drip pans through the openareas to reach the condenser above. In this embodiment, it is beneficialto increase the density of the condenser fins, or more particularly, toincrease the condenser surface area and/or condenser tubing directlyover the condensate drip pans so as to increase the amount of condensatedrip into the pans. Condensate drops that form elsewhere simply dripback down into the coolant pool, without being directed towards the atleast partially non-immersed electronic components to be cooled.

Advantageously, the embodiment of FIGS. 8A & 8B is simpler andpotentially less expensive to manufacture than the embodiment describedabove in connection with FIGS. 7A & 7B, due to the use of standardmaterials for the mesh and drip pans. However, this embodiment doesemploy a modified vapor condenser to encourage preferential condensationdrops over certain regions of the board, and a certain amount of thecondensate drip will not be collected and preferentially dripped backtowards the at least partially non-immersed electronic components.

FIGS. 9A & 9B show another alternate embodiment of a cooled electronicsystem 900, comprising a cooling apparatus in accordance with one ormore aspects of the present invention. In this embodiment, the coolingapparatus includes a liquid-cooled vapor condenser 910 and a condensateredirect structure 940, which in one embodiment, may comprisespecially-configured drip pans (such as depicted in FIG. 9B). Condensateredirect structure 940 is suspended via suspension structures 941 sothat its upper surface 942 is angled or sloped from a first side 945 toa second side 946 of condensate redirect structure 940. As condensatemoves from the first side to the second side of the condensate redirectstructure, it drips through openings 943 provided in one or morechannels or condensate transport regions 942 of condensate redirectstructure 940. As in the above-described cooling apparatus embodiments,condensate drip is preferentially provided over one or more at leastpartially non-immersed electronic components of the electronic systembeing partially immersion-cooled. This is achieved by, in oneembodiment, configuring condensate redirect structure with a desiredpattern of channels or condensate transport regions 942, and condensatedrip openings 943 therein, so that the desired patterns of condensatedrip are achieved. Note that the embodiment depicted in FIG. 9B is oneembodiment only of this concept. Also, note that in this example,different numbers of condensate drip openings may be provided over thedifferently configured, at least partially non-immersed electroniccomponents to be cooled.

As illustrated in FIG. 9A, condensate collection and preferential dripis further facilitated by providing vapor condenser 910 with one or moresloped, thermally conductive fins 912 that facilitate movement ofcondensed coolant drops in a first direction 915 for dropping ontocondensate redirect structure 940 at first side 945 thereof, wherein thecondensate redirect structure 940 is suspended to facilitate movement ofthe condensate in a second direction 916 along the condensate redirectstructure. In the embodiment depicted, the second direction is differentfrom the first direction, and more particularly, is opposite to thefirst direction.

In the embodiment depicted in FIGS. 9A & 9B, condensate collected at,for example, first side 945, is redirected and dripped back onto the atleast partially non-immersed electronic components to be cooled. Thecondensate redirect structure may include or be fabricated as a drip panthat includes a plurality of connected channels such that condensatedrops collected at the first side of the structure flow along thedifferent channels or condensate transport regions, dripping over the atleast partially non-immersed electronic components to be cooled as theydo. The shape of the channels (or condensate transport regions), as wellas the shape and number of condensate drip openings and density,determine how much condensed coolant drips over particular partiallynon-immersed electronic components. The vapor condenser with the sloped,thermally conductive condenser fin(s) also encourages condensate dropsthat have condensed elsewhere to flow towards the first side ofcondensate redirect structure 940 for accumulating and dripping back, asdescribed above. A wettability gradient may also be applied, forexample, from the left side (liquid-phobic) to the right side(liquid-philic) to improve the flow of condensed liquid along thecondenser fin(s) towards the first side of the condensate redirectstructure.

Similar to the embodiment of FIGS. 8A & 8B described above, the solutionof FIGS. 9A & 9B is potentially easier to manufacture due to the use ofstandard materials, but requires the condenser to also be modified.Unlike the embodiment of FIGS. 7A & 7B, not all of the condensate willbe preferentially dripped back over the non-immersed electroniccomponents to be cooled. That is, a certain amount of the condensatedrops will return directly to the coolant pool without interacting withthe non-immersed components.

FIG. 10 depicts one embodiment of a liquid-cooled electronic system 1000comprising a liquid-cooled electronics rack 1001 with a plurality ofpartially immersion-cooled electronic systems 1010 disposed, in theillustrated embodiment, horizontally, so as to be stacked within therack. By way of example, each electronic system 1010 may be a serverunit of a rack-mounted plurality of server units. In addition, eachelectronic system may include multiple electronic components to becooled, which in one embodiment could comprise multiple different typesof electronic components having different heights and/or shapes withinthe electronic system.

By way of example, the cooling system comprises one or more coolingapparatuses such as described above in connection with FIGS. 7A-9B. Inparticular, each cooling apparatus 1015 surrounds and forms acompartment about multiple electronic components of the electronicsystem 1010 to be cooled, and a vapor condenser comprises aliquid-cooled structure with, in one embodiment, a serpentine coolantchannel 1017 passing therethrough. Fluid vapor rising to the upperregion of the compartment is condensed into condensate drops and fallsback onto the condensate redirect structure, such as described above inconnection with the embodiments of FIGS. 7A-9B. The cooling apparatusfurther includes one or more modular cooling units (MCUs) 1020 disposed,by way of example, in a lower portion of electronics rack 1001. Eachmodular cooling unit 1020 may be similar to the modular cooling unitdepicted in FIG. 4, and described above. The modular cooling unit 1020includes, for example, a liquid-to-liquid heat exchanger 1021 forextracting heat from system coolant flowing through a system coolantloop 1030 of the cooling apparatus, and dissipating heat within afacility coolant loop 1025, comprising a facility coolant supply lineand a facility coolant return line. As one example the facility coolantsupply and return lines couple modular cooling unit 1020 to a datacenter facility coolant supply and return (not shown). Modular coolingunit 1020 further includes an appropriately sized reservoir 1022, pump,and optional filter (not shown), for moving liquid coolant underpressure through system coolant loop 1030. In one embodiment, systemcoolant loop 1030 includes a coolant supply manifold 1031, and a coolantreturn manifold 1032, which facilitate flow of system coolant (e.g.,water) through, for example the liquid-cooled vapor condensers of thecooling apparatuses 1015 disposed to cool the electronic components ofthe electronic systems 1010.

As a further enhancement, disclosed hereinbelow with reference to FIGS.11-15C, is a cooling apparatus, wherein partial immersion-cooling isemployed in combination with one or more wicking film elementsphysically contacting one or more selected surface(s) of one or more atleast partially non-immersed electronic components of the electronicsystem to be cooled (such as a server). These one or more non-immersedcomponents may be taller electronic components that are only partiallyimmersed, or may be electronic components suspended within theelectronic system such that they are completely non-immersed within thedielectric fluid. The cooling apparatuses and methods disclosed hereinfacilitate drawing or wicking of the dielectric fluid into closeproximity to the at least partially non-immersed components tofacilitate cooling thereof via evaporation of the dielectric fluid.Although illustrated in combination with the cooling apparatus of FIG.7, the cooling apparatus of FIG. 11, with the wicking film elementsphysically coupled to selected components of the electronic system, maybe employed, if desired, without a condensate redirect structure, and/orwith different types of vapor condensers.

Generally stated, disclosed herein is an alternate embodiment of acooling apparatus which includes a housing at least partiallysurrounding and forming a compartment about multiple components to becooled, and a fluid (such as a dielectric fluid) disposed within thecompartment. A component of the multiple components is at leastpartially non-immersed within the fluid, and a wicking film elementphysically contacts a main surface of the component, and is partiallyimmersed within the fluid disposed within the compartment. A couplingelement holds the wicking film element in physical contact with the mainsurface of the component without the coupling element overlying the mainsurface of the component.

One embodiment of such a cooling apparatus is illustrated in FIG. 11.This cooling apparatus 700′ comprises a cooling apparatus similar tothat described above in connection with FIGS. 7A-7B, with the additionof multiple wicking film elements 1100, 1110 in physical contact withdifferently configured, at least partially non-immersed components ofthe electronic system. By way of specific example only, in oneembodiment, electronic component 721 may comprise multiple DIMMs, eachwith multiple chips 1101 disposed on opposite main sides of therespective component board. Respective wicking film elements 1100overlie the main sides of the component boards, and in particular, themain surfaces 1102 of the chips affixed to the different sides of thecomponent boards. The wicking film elements are (in one embodiment) inphysical contact with respective main surfaces 1102 of chips that theelements overlie.

Additionally, in this embodiment, a differently configured component 722includes a plurality of thermally conductive fins 1111 projecting abovethe dielectric fluid, and thus, at least partially non-immersed withinthe dielectric fluid. To facilitate cooling of these thermallyconductive fins, the cooling apparatus further includes wicking filmelements 1110 that are differently configured from wicking film elements1100. In accordance with an aspect of the present invention, the wickingfilm elements for different components may be differently configuredand/or fabricated. For example, the wicking film elements 1100 may havea thickness greater than the wicking film elements 1110 in theheterogeneous electronic system example of FIG. 11. Different grades andvarieties of porous materials may also be used, depending on thecomponent to be cooled. In this manner, the wicking film elements may becustomized for the particular, at least partially non-immersedelectronic component to be cooled within the heterogeneous electronicsystem. As illustrated, each wicking film element 1110 wraps over arespective thermally conductive fin structure 1111 to facilitateevaporative cooling of the fin. As depicted in FIG. 11, wicking filmelements 1100 and wicking film elements 1110 are differently configured,and facilitate wicking of dielectric fluid towards the different typesof differently configured components 721, 722.

Each wicking film element comprises, in one embodiment, a porous wickstructure, such as a porous film. More particularly, one or more of thewicking film elements might be fabricated of porous metal (such asporous silver, porous copper, porous aluminum, or sintered copper),porous glass, porous ceramics (such as porous titania or zirconia), orporous polymer (such as porous polyethersulphone (PES) or nylon). By wayof specific example, the wicking films could comprise a film fabricatedof copper foam, such as marketed by Metafoam, of Brossard, Quebec,Canada, or porous silver, or porous nylon, both of which are availablethorugh Millipore, of Billerica, Mass., U.S.A. The wicking film isfabricated of a high-temperature-tolerant material, and is a porous,dielectric fluid-philic material. By way of specific example, thewicking film elements might have a pore size of microns or smaller toprovide the sufficient capillary force to draw the dielectric fluidupwards. Thickness of the film can vary, depending upon the application.In one example, film thickness is less than 5 millimeters, and moreparticularly, less than or equal to 1 millimeter. Height of the wickingfilm element can vary, depending upon the height of the component to becooled, with one to two inches being exemplary. In one embodiment, aportion of the wicking film element, such as 25% of the wicking filmelement, is disposed within the dielectric fluid in the compartment.Those skilled in the art will understand that the particularconfiguration, including film thickness, porosity, and pore size, willdepend on the type of dielectric fluid employed and the surface tensionof the dielectric fluid used. Thus, the wicking film element material,structure, and dielectric fluid to be employed, may be experimentallydetermined for a particular application.

The porous wick structures wick the dielectric fluid by capillary force,and bring the fluid close to the non-immersed surfaces of the at leastpartially non-immersed components. The heat of the components causes thefluid within the porous wick structures (or films) to evaporate away,thus assisting in cooling the heated chips or surfaces. The evaporateddielectric vapor egresses from the wicking film, condenses on contactwith the condenser surfaces, and drips back to the fluid pool in thelower portion of the enclosure via, by way of example, the condensateredirect structure 740.

FIGS. 12A & 12B depict one embodiment of coupling elements for holdingthe wicking film element in physical contact with respective mainsurfaces 1102 of, for example, the chips 1101 mounted to opposite sidesof the component board, without the coupling elements overlying the mainsurfaces of the chips to be cooled. In this embodiment, adhesive lines1200 are employed as the coupling element. This adhesive, which may (forinstance) be a thermal adhesive, attaches to the wicking film elementsalong the edges of the chips (i.e., at the edges of the main surfaces ofthe chips). By attaching the adhesive only to the wicking film elementsat the edges of the chips, the coupling element (e.g., adhesive, such asepoxy, solder, etc.) does not overlie the heated surfaces physicallycontacted by the wicking film elements.

Note that although shown in FIGS. 12A & 12B with uniform height, width,and thickness, the wicking film elements 1100 physically couple to themain surfaces of the chips to be cooled may be differently configured,and even have different compositions depending, for example, on thenumber and types of chips disposed on opposite sides of the componentboard.

FIGS. 13A & 13B depict another embodiment of a component 1305, such as aDIMM component of an electronic system (not shown), that is partiallynon-immersed within a fluid disposed within a compartment such asillustrated in FIG. 11. Note that in the example of FIGS. 13A & 13B, thewicking film element 1300 is assumed to be at least partially immersedwithin the dielectric fluid within the compartment that the componentresides. In this implementation, the wicking film element 1300 comprisesa material such as described above and is sized to wrap over component1305 so as to be physically coupled to multiple chips 1301 disposed onopposite sides of the component 1305. Wicking film element 1300 isconfigured to facilitate wicking of dielectric fluid towards the mainsurfaces of the chips 1301, and heat dissipated by the chips causes thefluid within the wicking film element to evaporate away, thus assistingcooling of the chips. As in the above examples, each wicking filmelement may be, in one embodiment, a porous wick structure, such as aporous film made of sintered metal or (for example) a high-temperaturepolymer, such as porous coolant-philic nylon or porous carbonpaper/film. The wicking film element has a length such that when wrappedover component 1305, the ends of wicking film element reside within thedielectric fluid within the compartment.

In this embodiment, the coupling element 1310 comprises a clip, which inone embodiment is a U-shaped, spring clip. Clip 1310 includes aplurality of clip openings 1311, 1312, 1313, which are sized andpositioned to align over the respective multiple chips 1301 disposed onopposite sides of component 1305. By configuring and positioning clipopenings 1311, 1312, 1313, to overlie the multiple chips 1301,outwardly-egressing dielectric fluid vapor from the film is unimpeded bythe clip. The clip 1310 applies a mechanical pressure to wicking filmelement 1300 wrapped over component 1305, and presses the wicking filmelement into physical contact with the heated chips (or surfaces) of thecomponent. In one embodiment, the wicking film element has somemechanical stiffness, for example, being fabricated of a porous metalfilm or porous polymer. Configuration of the clip to not overlie theunderlying chips being cooled, facilitates egressing of dielectric fluidvapor from the wicking film element in the region of the chips, whichlimits the possibility of vapor building up within the film.

FIGS. 14A & 14B depict another embodiment of a coupling element 1410 forphysically coupling wicking film element 1300 to, for example, multiplechips 1301 on opposite sides of component 1305 of an electronic system,for example, such as depicted in FIG. 11. In this embodiment, couplingelement 1410 comprises a clip, such as a U-shaped, spring clip, which issized and configured to securely couple in physical contact wicking filmelement 1300 to the heated surfaces of component 1305, such as the mainsurfaces of chips 1301 disposed on the opposite sides of the component.In this configuration, coupling element 1410 comprises an outer frame1411 with large first and second clip openings 1412 at opposite mainsides of the component 1305. A screen 1413 resides within the first andsecond clip openings 1412 at the opposite main sides of the component.These screens facilitate securing the wicking film element 1300 inphysical contact with the surfaces to be evaporatively cooled by wickingof the dielectric fluid into close proximity to the surfaces. Note thatin this embodiment, the screens 1413 include relatively large openings1414 sized to minimize impeding of egressing fluid vapor from thewicking film element, for example, in the evaporation regions over thechips 1301.

FIGS. 15A-15B depict another embodiment of an electronic component 1505of an electronic system partially immersion-cooled, in accordance withone or more aspects of the present invention. This electronic componentcould comprise part of an electronic system such as depicted in FIG. 11,and described above. The component 1505 is analogous to that describedabove in connection with FIGS. 12A-14B, however, the chips 1501 onopposite main sides of component 1505 are assumed in this example to bedifferently-sized and configured, and may be (for example) differenttypes of chips providing different functions within the electronicsystem. In this embodiment, the wicking film elements 1500, 1500′ forthe different sides of component 1505 are differently configured, forexample, to accommodate the differently configured chips 1501 disposedon the opposite main sides of the component. By partially encircling andfilling the spaces between the edges of the multiple chips 1501, thewicking film elements 1500, 1500′ facilitate bringing dielectric fluidinto close proximity to all heated surfaces of the component. Note thatin one implementation, the wicking film elements 1500, 1500′ may befabricated of a more rigid material, and include recess regions for therespective chips to be evaporatively cooled by the dielectric fluid. Inthis embodiment, the coupling element 1510 comprises a plurality ofU-shaped clips, which as noted in FIG. 15C, are (in one embodiment)sized and configured so as not to overlie the multiple chips 1501 on theopposite sides of the component 1505. By avoiding overlying the chips,the U-shaped clips assist in securely physically coupling the wickingfilm elements 1500, 1500′ to the respective sides of the component,without inhibiting egress of dielectric fluid vapor from the wickingfilm elements in the region of the underlying chips being cooled.

Advantageously, the porous wicking film elements disclosed herein wickthe dielectric fluid from a lower level of the compartment, drawing thedielectric fluid to the heated components and surfaces non-immersedwithin the dielectric fluid. The wicked fluid evaporates from thewicking film elements to help cool the associated heated components.This process of evaporation causes more fluid to be wicked up the porousfilm elements, ensuring continued cooling. The use of porous wickingfilms to draw and then evaporate the immersion-cooling fluid helps toreduce the amount of fluid necessary to fill the enclosure, since thetaller components (i.e., non-immersed components) do not have to beimmersed to be cooled by the vaporizing coolant. The reduction indielectric fluid in turn helps to reduce the cost and weight of thecooling solution described. In addition to this advantage,immersion-cooling has several inherent advantages, including improvedtemperature uniformity across various, different components of anelectronic system, lower required flow rate of the secondary fluidthrough the vapor condenser, and the potential for warm water cooling.This latter advantage improves energy efficiency, and enables the use ofeconomizers.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprise” (andany form of comprise, such as “comprises” and “comprising”), “have” (andany form of have, such as “has” and “having”), “include” (and any formof include, such as “includes” and “including”), and “contain” (and anyform contain, such as “contains” and “containing”) are open-endedlinking verbs. As a result, a method or device that “comprises”, “has”,“includes” or “contains” one or more steps or elements possesses thoseone or more steps or elements, but is not limited to possessing onlythose one or more steps or elements. Likewise, a step of a method or anelement of a device that “comprises”, “has”, “includes” or “contains”one or more features possesses those one or more features, but is notlimited to possessing only those one or more features. Furthermore, adevice or structure that is configured in a certain way is configured inat least that way, but may also be configured in ways that are notlisted.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below, if any, areintended to include any structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of the present invention has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the invention in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the invention.The embodiment was chosen and described in order to explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention throughvarious embodiments and the various modifications thereto which aredependent on the particular use contemplated.

What is claimed is:
 1. A cooling apparatus comprising: a housing atleast partially surrounding and forming a compartment about multiplecomponents to be cooled; a fluid disposed within the compartment,wherein a component of the multiple components is at least partiallynon-immersed within the fluid; a wicking film element physically coupledto a main surface of the component and partially disposed within thefluid disposed within the compartment; and a coupling element physicallycoupling the wicking film element to the main surface of the componentwithout the coupling element overlying the main surface of thecomponent.
 2. The cooling apparatus of claim 1, wherein the componentcomprises a chip, and wherein the coupling element resides at an edge ofthe chip, and secures the wicking film element to the chip at the edgeof the chip.
 3. The cooling apparatus of claim 1, wherein the wickingfilm element wraps over at least a portion of the component.
 4. Thecooling apparatus of claim 3, wherein the component comprises at leastone thermally conductive fin extending therefrom and at least partiallynon-immersed within the fluid, and wherein the wicking film elementwraps over the at least one thermally conductive fin extending from thecomponent.
 5. The cooling apparatus of claim 3, wherein the componentcomprises a component board with a first side and a second side, thefirst side and the second side being opposite sides of the componentboard, and wherein at least one chip resides on the first side of thecomponent board and at least one chip resides on the second side of thecomponent board, and wherein the wicking film element wraps over thecomponent board and physically contacts the at least one chip on thefirst side of the board and the at least one chip on the second side ofthe board.
 6. The cooling apparatus of claim 5, wherein the couplingelement comprises at least one clip extending over the component boardand holding the wicking film element in physical contact with the atleast one chip on the first side of the component board and in physicalcontact with the at least one chip on the second side of the componentboard without overlying the at least one chip on the first side of thecomponent board or the at least one chip on the second side of theboard.
 7. The cooling apparatus of claim 6, wherein the component boardcomprises multiple chips on the first side thereof and multiple chips onthe second side thereof, and wherein the at least one clip is configuredwith at least one first clip opening over the multiple chips on thefirst side of the component board and at least one second clip openingover the multiple chips on the second side of the component board, theat least one first clip opening over the first side of the componentboard and the at least one second clip opening over the second side ofthe component board respectively facilitating egress of evaporated fluidfrom the wicking film element in regions thereof overlying the multiplechips on the first side of the component board and the multiple chips onthe second side of the component board.
 8. The cooling apparatus ofclaim 7, wherein the at least one clip further comprises at least onefirst screen within the at least one first clip opening over themultiple chips on the first side of the component board and at least onesecond screen within the at least one second clip opening over themultiple chips on the second side of the board, the at least one firstscreen and the at least one second screen comprising screen openingssized to facilitate egress of evaporated fluid from the wicking filmelement disposed between the at least one clip and the multiple chips onthe first side of the component board and the multiple chips on thesecond side of the component board.
 9. The cooling apparatus of claim 1,wherein the component comprises a first component, and wherein a secondcomponent of the multiple components is at least partially non-immersedwithin the fluid, the first component and the second component beingdifferently configured components, and wherein the wicking film elementcomprises a first wicking film element coupled to the first component,and the cooling apparatus further comprises a second wicking filmelement coupled to the second component, the first and second wickingfilm elements being at least partially immersed within the fluiddisposed within the compartment, and wherein the first wicking filmelement and the second wicking film element are differently configured,and facilitate wicking of fluid towards the differently configured firstcomponent and second component.
 10. The cooling apparatus of claim 9,wherein the first wicking film element wraps over the first componentcovering at least a portion of a first side and a second side of thefirst component, wherein the first side and second side are oppositemain sides of the first component.
 11. A liquid-cooled electronic systemcomprising: an electronic system comprising multiple electroniccomponents to be cooled; a cooling apparatus partially immersion-coolingthe electronic system, the cooling apparatus comprising: a housing atleast partially surrounding and forming a compartment about the multipleelectronic components to be cooled; a fluid disposed within thecompartment, wherein an electronic component of the multiple electroniccomponents is at least partially non-immersed within the fluid; awicking film element physically coupled to a main surface of theelectronic component and partially disposed within the fluid disposedwithin the compartment; and a coupling element physically coupling thewicking film element to the main surface of the component without thecoupling element overlying the main surface of the component.
 12. Theliquid-cooled electronic system of claim 11, wherein the componentcomprises a chip, and wherein the coupling element resides at an edge ofthe chip, and secures the wicking film element to the chip at the edgeof the chip.
 13. The liquid-cooled electronic system of claim 11,wherein the wicking film element wraps over at least a portion of theelectronic component, and wherein the electronic component comprises atleast one thermally conductive fin extending therefrom and at leastpartially non-immersed within the fluid, and wherein the wicking filmelement wraps over the at least one thermally conductive fin extendingfrom the electronic component.
 14. The liquid-cooled electronic systemof claim 13, wherein the component comprises a component board with afirst side and a second side, the first side and the second side beingopposite sides of the component board, and wherein at least one chipresides on the first side of the component board and at least one chipresides on the second side of the component board, and wherein thewicking film element wraps over the component board and physicallycontacts the at least one chip on the first side of the board and the atleast one chip on the second side of the board.
 15. The liquid-cooledelectronic system of claim 14, wherein the coupling element comprises atleast one clip extending over the component board and holding thewicking film element in physical contact with the at least one chip onthe first side of the component board and in physical contact with theat least one chip on the second side of the component board withoutoverlying the at least one chip on the first side of the component boardor the at least one chip on the second side of the board.
 16. Theliquid-cooled electronic system of claim 15, wherein the component boardcomprises multiple chips on the first side thereof and multiple chips onthe second side thereof, and wherein the at least one clip is configuredwith at least one first clip opening over the multiple chips on thefirst side of the component board and at least one second clip openingover the multiple chips on the second side of the component board, theat least one first clip opening over the first side of the componentboard and the at least one second clip opening over the second side ofthe component board respectively facilitating egress of evaporated fluidfrom the wicking film element in regions thereof overlying the multiplechips on the first side of the component board and the multiple chips onthe second side of the component board.
 17. The liquid-cooled electronicsystem of claim 16, wherein the at least one clip further comprises atleast one first screen within the at least one first clip opening overthe multiple chips on the first side of the component board and at leastone second screen within the at least one second clip opening over themultiple chips on the second side of the board, the at least one firstscreen and the at least one second screen comprising screen openingssized to facilitate egress of evaporated fluid from the wicking filmelement disposed between the at least one clip and the multiple chips onthe first side of the component board and the multiple chips on thesecond side of the component board.
 18. The liquid-cooled electronicsystem of claim 11, wherein the component comprises a first component,and wherein a second component of the multiple components is at leastpartially non-immersed within the fluid, the first component and thesecond component being differently configured components, and whereinthe wicking film element comprises a first wicking film element coupledto the first component, and the cooling apparatus further comprises asecond wicking film element coupled to the second component, the firstand second wicking film elements being at least partially immersedwithin the fluid disposed within the compartment, and wherein the firstwicking film element and the second wicking film element are differentlyconfigured, and facilitate wicking of fluid towards the differentlyconfigured first component and second component.
 19. The liquid-cooledelectronic system of claim 18, wherein the first wicking film elementwraps over the first component covering at least a portion of a firstside and a second side of the first component, wherein the first sideand second side are opposite main sides of the first component.
 20. Amethod of facilitating cooling of an electronic system, the methodcomprising: providing a housing at least partially surrounding andforming a compartment about multiple electronic components of theelectronic system; providing a fluid disposed within the compartment,wherein an electronic component of the multiple components is at leastpartially non-immersed within the fluid; providing a wicking filmelement physically coupled to a main surface of the electronic componentand partially disposed within the fluid disposed within the compartment;and securing, via a coupling element, the wicking film element inphysical coupling to the main surface of the component without thecoupling element overlying the main surface of the component.